Automatic regulation of electrochemical machining systems

ABSTRACT

This device for the automatic regulation of electrochemical machining processes is adapted to modify machining conditions according to the nature of the surface being machined and the rate of tool feed. It comprises temperature measuring means inserted in each electrolyte discharge conduit and adapted to control through servo means the output adjustment members. This device is applicable to the regulation of machining conditions by varying the return electrolyte output in machines of the type comprising an electrolyte-filled chamber under pressure.

United States Patent Fleury et al.

[54] AUTOMATIC REGULATION OF ELECTROCHEMICAL MACHINING SYSTEMSInventors: Jean Fleul'y; Jean Pinot, both of Biliancourt, FranceAssignees: Regie Nationale Des Usines Renaults, Billancourt; AutomobilesPeugeot, Paris, France Filed: Feb. 16,1971

Appl.No.: 115,426

Foreign Application Priority Data 2 Feb. 18, 1970 France ..70057s0 U.S.Cl ..204/224, 204/229 ..B23p 1/02, BOlk 3/04 ..204/224, 225, 229, 143 MReferences Cited UNITED STATES PATENTS Dickson.... ..204 224 xWilliams...

[ June 27, 1972 FOREIGN PATENTS OR APPLICATIONS 38/l2,829 7/1963 Japan..204/224 38/l3,764 7/1963 Japan.... .....204/224 {ii/18,487 10/1966Japan ..204/l43 M Primary Examiner-John H. Mack Assistant Examiner-D. R.Valentine AttorneyStevens, Davis, Miller & Mosher ABSTRACT 7 Claims, 1Drawing Figure AUTOMATIC REGULATION OF ELECTROCHEMICAL MACHINING SYSTEMSThe present invention relates to means for automatically regulating theoperating conditions of an electrode-tool in an electrochemicalmachining process.

In machines designed for electrochemical machining processes theworkpiece material is removed electrolytically by causing aunidirectional electric current to flow between an anode-workpiece and acathode-tool across an electrolyte circulating in the space providedbetween workpiece and tool.

The precision and reproductibility of an electrochemical machiningoperation are subordinate to the stability of operating conditionsprevailing in the space left between workpiece and tool. Therefore,these conditions vary as a function of the evolution of the geometry ofthe machined surface and also of the physical changes occurring in theelectrolyte proper, i.e. either an output reduction and a increment bothin temperature and the electrolyte iron hydroxide contents as a functionof the increment in the surface areas involved (loss of pressure).

The parameters controlling the values of the machining gap are thevoltage applied to the tool and workpiece, the tool feed rate and theelectrolyte current conductivity.

- The first two parameters are generally kept at constant values or atleast easily adjusted. It has been endeavoured to keep the conductivityof the electrolyte at a constant value by stabilizing its temperatureand possibly modifying this temperature as a function of compositionvariations. Arrangements of this character comprise means for directlymeasuring the conductivity in conjunction with a temperature regulatingdevice responsive to the apparatus provided for measuring theelectrolyte conductivity and the electrolyte concentration.

As a result, these installations are both sophisticated and veryexpensive, and this temperature regulation method is attended by acertain response inertia or lag.

Arrangements are also known wherein the machining rate is adjusted byvarying the-electrolyteoutput at different points of the machinedsurface. The output evolution is adjusted in this case as a function ofa predetermined program. However, also in this arrangement the programis costly to develop and achieve, and the versatility and flexibility ofoperation is rather questionable.

The present invention is directed to means capable of achieving anoutput regulation as a function of the evolution of the machinedsurfaced by controlling directly the electrolyte temperature.

It is therefore the essential object of the present invention to providea device for regulating the electrolyte output in the specific case ofthe machining of workpieces in a pressurized chamber comprising meansfor measuring the temperature in each return duct for the electrolyteflow, said means controlling in turn the output adjustment memberscorresponding to each return duct.

Another object of this invention consists in arranging said temperaturemeasuring means in the workpiece carrier tray and coating the innerwalls of the electrolyte return ducts with a suitable head-insulatingmaterial between the machining area and the point where the temperatureis measured.

Provided only that the losses of pressure in the machining area at theinlet of each electrolyte return duct remain constantly inferior tothose of the corresponding output adjustment valve, the presentinvention will thus constitute an automatic machining regulating system.When the electrolyte temperature rises as a consequence of a reductionin electrolyte output due to the increase in the machined surface area,the temperature measuring means determines an increase in thecross-sectional passage area of the output adjustment valve. Thus, theincreased electrolyte output restores the temperature to its initialvalue and the state of equilibrium controlling the amount of electrolyteper surface unit is also restored to its initial value.

In addition to its considerable simplicity, the arrangement according tothe present invention is advantageous in that it achieves a continuousregulation of the machining process without requiring any preliminarywork programming procedure, thus affording a considerable simplificationin the general arrangement of the machine and a greater flexibility foradapting same to the most diversified types of machining operations,since only the tools are to be changed. The range of workingtemperatures contemplated for the electrolyte will determineautomatically the electrolyte output adjustment at different points ofthe surface to be machined.

A typical and exemplary form of embodiment of a device constructedaccording to the teachings of this invention will now be described withreference to the attached drawing of which the single FIGURE illustratesdiagrammatically in section an electrode-tool assembly during amachining operation.

A cathode-tool l is secured to an electrode carrier tray 2 rigid with aguiding column 3. In the figure the tool 1 is shown in its position ofengagement at the beginning of a machining operation to be performed ona workpiece 4. The pressure chamber is shown diagrammatically by achain-dotted line 5.

The electrolyte 6 is supplied under pressure to chamber 5 via inletducts 7 opening either directly into said pressure chamber 5 or throughcolumn 3 and tray 2, and through the tool 1, into preferential areas ofthe tool surface.

The electrolyte is discharged or returned through ducts 8 openinglikewise into the tool surface in preferential machining areas, so as torise through the tool 1 and tray 2 along column 3. These ducts 8 arecontinued by pipe-lines receiving output regulating valves 9 to theapparatus for recovering and regenerating the electrolyte (by regulationand cleaning, etc.) not shown, from which the electrolyte is recycledthrough the tool 1 via ducts 7.

In the area corresponding to the passage through the tool 1 the innerwalls of ducts 8 are coated with a lining 10 of heatinsulating material.This lining may consist of a layer of plastic material applied byimmersion or any other equivalent method. Alternatively, sections ofplastic tubes may be driven through corresponding holes formed throughthe tool means.

Thermocouples II are disposed within the ducts 8 and their ends areflush with the surface of the tool-supporting tray 2, the ends of theducts 8 of tool 1 being head-insulated. These thermocouples areconnected to regulating amplifiers I2 controlling through servo-relays13 the degree of opening of the output adjustment valves 9.

During the operation, when the temperature of the electrolyte rises, forexample in the machining areas 14, this temperature increment istransmitted without any appreciable variation, due to theheat-insulating lining 10, to the thermocouples ll controlling theregulating amplifiers 12. When the temperature exceeds a predeterminedor preset maximum or limit value, the amplifiers 12 control viaservo-relays 13 the opening of output regulating valves 9. The resultingincrement in the electrolyte output is attended by the return to theselected initial temperature value, thus restoring the equilibriumcorresponding to the proper amount of electrolyte per surface unit.Under these conditions, it is clear that for a given tool feed rate aself-regulation of the machining conditions will be achieved byadjusting the electrolyte output in the different areas as a function ofthe detected variations in the local temperature.

An output (the same in each return duct 8), though low it may be, isalways necessary for providing a reference datum to regulating device.The output increment in each duct 8 varies without any interference fromone duct to another and only as a function of the local evolution of themachined surfaces.

The provision of thermocouples 11 within the tray 2, well recessed fromthe tool means 2, afiords a rapid and easy replacement of these toolmeans without any risk of damaging the thermocouples since these are nothandled during this tool substitution.

Although a single fonn of embodiment has been described hereinabove withreference to the attached drawing, it will readily occur to thoseconversant with the art that various modifications may be broughtthereto without departing from the spirit and scope of the invention asset forth in the appended claims.

What is claimed as new is 1. Device for automatically regulating theelectrochemical machining of workpieces in machines wherein the tooloperated within a pressurized chamber filled with electrolyte, said toolcomprising duct means for supplying and discharging the electrolyte,characterized in that temperature measuring means are inserted in eachelectrolyte discharge duct and adapted to control through servo meanselectrolyte adjustment means inserted in the corresponding dischargeducts.

2. Automatic regulating device according to claim 1, wherein thetemperature measuring means consist of thermocouples disposed within theelectrolyte discharge ducts.

3. Automatic regulating device according to claims 1 and 2, wherein thepoints where the electrolyte temperature is measured are located withina tool-carrier tray at the level of the tool mounting surface.

4. Automatic regulating device according to claim 3, wherein theelectrolyte discharge ducts extend through said tool and haveheat-insulated inner walls.

5. Automatic regulating device according to claim 4, wherein the heatinsulation of the inner walls of said electrolyte discharge ductsconsists of a plastic coating applied by immersion.

6. Automatic regulating device according to claim 4, wherein said heatinsulation consists of plastic tube sections inserted in thecorresponding holes formed in the tool means for constituting saidelectrolyte discharge ducts.

7. Automatic regulating device according to claim 1, wherein the outputadjustment means consist of solenoidoperated valves and said servo-meanscomprise a regulatingamplifier and a servo-relay.

1. Device for automatically regulating the electrochemical machining ofworkpieces in machines wherein the tool operated within a pressurizedchamber filled with electrolyte, said tool comprising duct means forsupplying and discharging the electrolyte, characterized in thattemperature measuring means are inserted in each electrolyte dischargeduct and adapted to control through servo means electrolyte adjustmentmeans inserted in the corresponding discharge ducts.
 2. Automaticregulating device according to claim 1, wherein the temperaturemeasuring means consist of thermocouples disposed within the electrolytedischarge ducts.
 3. Automatic regulating device according to claims 1and 2, wherein the points where the electrolyte temperature is measuredare located within a tool-carrier tray at the level of the tool mountingsurface.
 4. Automatic regulating device according to claim 3, whereinthe electrolyte discharge ducts extend through said tool and haveheat-insulated inner walls.
 5. Automatic regulating device according toclaim 4, wherein the heat insulation of the inner walls of saidelectrolyte discharge ducts consists of a plastic coating applied byimmersion.
 6. Automatic regulating device according to claim 4, whereinsaid heat insulation consists of plastic tube sections inserted in thecorresponding holes formed in the tool means for constituting saidelectrolyte discharge ducts.
 7. Automatic regulating device according toclaim 1, wherein the output adjustment means consist ofsolenoid-operated valves and said servo-means comprise aregulating-amplifier and a servo-relay.